STATEN ISLAND, N.Y. -- A suspicious package spotted outside a Randall Manor home Thursday afternoon sparked a large emergency response that left residents and parents of students who attend a nearby school fearing the worst.

The unattended backpack — found a day after the Sept. 11 anniversary by a black Toyota on Brentwood Avenue — contained what police have deemed a “hoax device.” It was the second non-explosive device made to resemble a bomb found on Staten Island in the past two weeks.

Firefighters and police units, including the Emergency Service Unit and the Bomb Squad, descended on the neighborhood around 1 p.m. and sealed off Brentwood, as well as Henderson Avenue, between Westbury Avenue and Lois Place. Some residents of Brentwood were asked to leave their homes.

A Bomb Squad unit clad in heavy dark green protective suits, along with other officers, retrieved the backpack outside of 11 Brentwood Ave.

Police determined the bag to be a “hoax device,” according to Det. Joseph Cavitolo, a spokesman for the NYPD, about an hour after emergency workers arrived.

Police are still investigating the incident.

Residents in the area expressed concern about the finding in a neighborhood that’s often very quiet and peaceful.

“It’s scary,” said Gary Minervini, a Westbury Avenue homeowner. “This is a good neighborhood. It’s shocking to hear something like that.”

He credited responders for quickly arriving to the location.

“This is something that doesn’t happen in this neighborhood,” said Mary Orazem, who lives a block from Brentwood.

“I wonder why someone would do that. I can’t believe it,” added Brent Hayrynen, who lives on the corner of Westbury and Henderson.

The incident happened shortly before St. Peter’s High School for Boys’ 2:26 p.m. dismissal time, prompting parents to fear for their children’s safety.

“I’m a nervous wreck,” said Great Kills resident Sueann Agugliaro, after she was detoured by police.

John Fodera, principal of the school, said the NYPD alerted him and his staff of the situation and had a patrol car outside to inform parents of the incident.

Otherwise, dismissal “couldn’t have been smoother.”

“From our point of view here, it was perfectly quiet,” said Fodera.

The incident marks the second time in two weeks such a device caused panic.

On Sept. 2, a tense bomb scare in Port Richmond unfolded when cops discovered a suitcase on an uninhabited stretch of Barrett Avenue just behind the Forest Avenue Shoppers Town strip mall. It was apparently so convincing that members of the NYPD’s Community Affairs Bureau on the scene told residents its contents resembled a C4, a moldable, plastic explosive.